Polymer compositions comprising polyethylene with increased stability

Abstract

The present invention relates to a polymer composition comprising or consisting of: a) a composition comprising at least one ethylene-based polymer; b) an additive composition comprising a compound of formula I wherein each R is selected from 1, 1-dimethylpropyl or hydrogen, respectively; and c) 2, 2-bis (hydroxymethyl)-1, 3-propanediol, and a method for preparing the same. Such polymer compositions are suitably and stably used in recovery applications in which undesired formation of 2, 4-di-tert-butylphenol is prevented. # imgabs0 #

Description

[0001] The present invention relates to polymer compositions comprising polyethylene having increased stability, particularly increased stability when undergoing multiple melt processing steps. The present invention particularly relates to polymer compositions comprising recycled polyethylene.

[0002] While phosphite antioxidants may be suitable for providing a certain stabilizing effect to polyethylene-based polymer formulations, an adverse effect of using certain phosphite-containing compounds is the occurrence of certain degradation products. In specific applications, such as in food contact applications, the occurrence of certain by-products due to the stabilizing action (wherein the antioxidant compound may decompose) is not appropriate. In particular, the occurrence of 2,4-di-tert-butylphenol (CAS registration number: 96-76-4) is to be avoided as it is a controlled substance.

[0003] Accordingly, there is a need to obtain polyethylene-based formulations that are sufficiently stable for desired applications, including food contact applications, wherein the formation or release of 2,4-di-tert-butylphenol is avoided.

[0004] In particular, such stabilizing schemes may be suitable for polymer formulations containing recycled polymers, especially recycled polyethylene materials. Given the circularity of materials, there is an increasing need for solutions that help avoid the disposal of polymer materials after the end of their service life, for example, after using the products contained therein in packaging applications, and thus the stabilizing requirements for such polymer materials are becoming increasingly stringent; after all, reusing such polymer materials through the recycling process means that the polymer materials undergo both additional shaping processes (usually involving melt processing steps) and an extended service life. The polymer molecules need to be able to withstand additional harsh exposures over a long period without undergoing inappropriate degradation. To achieve this, the polymer molecules can be assisted by stability compounds.

[0005] Accordingly, it is an object of the present invention to provide polymer composition materials comprising ethylene-based polymers that are sufficiently stable to also be used in recycling applications, wherein the undesired formation of 2,4-di-tert-butylphenol is prevented.

[0006] This is now achieved by a polymer composition comprising or consisting of:

[0007] a) a composition comprising at least one ethylene-based polymer;

[0008] b) an additive composition comprising a compound of formula I:

[0009]

[0010] wherein each R is independently selected from 1,1-dimethylpropyl or hydrogen; and

[0011] c) 2,2 - bis(hydroxymethyl)-1,3-propanediol.

[0012] Such polymer compositions are suitably stabilized, preventing the formation of 2,4 - di - tert - butylphenol due to the decomposition of the stabilizer compound.

[0013] In the context of the present invention, the stability of the polymer composition can be understood as being reflected by its vinyl index. The vinyl index represents the amount of vinyl unsaturation in the polymeric material. The lower the amount of unsaturation, the more stable the properties of the material and the less prone the material is to degradation. The vinyl index can be calculated from the absorption spectrum obtained, for example, via Fourier transform infrared (FTIR) analysis in transmission mode. To obtain the value of the vinyl index based on the FTIR spectrum, the following equation is applied:

[0014]

[0015] where A 908 is the absorbance of a sample of the material composition at 908 cm -1 , A 933 is the absorbance at 933 cm -1 , A 1897 is the absorbance at 1897 cm -1 , and A 1986 is the absorbance at 1986 cm -1 .

[0016] The FTIR spectrum of the material to be tested can be tested, for example, according to the method of ASTM D5576 - 00(2006).

[0017] Preferably, the ethylene - based polymer has a density of ≥940 and ≤975 kg / m 3 , preferably ≥950 and ≤970 kg / m 3 , more preferably ≥950 and ≤965 kg / m 3 as determined according to ISO1183 - 1(2019).

[0018] The ethylene - based polymer can, for example, have a melt mass - flow rate (MFR2) of ≥0.1 and ≤5.0 g / 10 min, preferably ≥0.1 and ≤2.0 g / 10 min, more preferably ≥0.1 and ≤1.0 g / 10 min as determined according to ISO1133 - 1(2011) at 190 °C under a load of 2.16 kg.

[0019] The ethylene-based polymer may, for example, have a melt mass flow rate (MFR5) of ≥ 1.0 and ≤ 10.0 g / 10 min, preferably ≥ 1.0 and ≤ 7.5 g / 10 min, more preferably ≥ 1.5 and ≤ 5.0 g / 10 min, as measured at 190 °C under a load of 5 kg in accordance with ISO 1133-1 (2011).

[0020] The ethylene-based polymer may, for example, have a melt mass flow rate (MFR21) of ≥ 10 and ≤ 100 g / 10 min, preferably ≥ 20 and ≤ 75 g / 10 min, more preferably ≥ 25 and ≤ 60 g / 10 min, as measured at 190 °C under a load of 21.6 kg in accordance with ISO 1133-1 (2011).

[0021] For example, the ethylene-based polymer may be an ethylene homopolymer or an ethylene copolymer comprising structural parts of ≤ 10.0 wt%, preferably ≤ 5.0 wt% of comonomers derived from 1-butene, 1-hexene and 1-octene.

[0022] In the polymer composition according to the invention, composition a) preferably comprises a recycled polyethylene formulation. Particularly preferably, composition a) comprises ≥ 20.0 wt%, more preferably ≥ 40.0 wt% of a recycled polyethylene formulation, based on the total weight of composition a).

[0023] The recycled polyethylene formulation may, for example, be a post-consumer recycled polyethylene formulation. The recycled polyethylene formulation may, for example, have a density of ≥ 940 and ≤ 975 kg / m 3 、preferably ≥ 950 and ≤ 970 kg / m 3 、more preferably ≥ 950 and ≤ 965 kg / m 3 as measured in accordance with ISO 1183-1 (2019). The recycled polyethylene formulation may, for example, have a melt mass flow rate (MFR2) of ≥ 0.1 and ≤ 5.0 g / 10 min, preferably ≥ 0.1 and ≤ 2.0 g / 10 min, more preferably ≥ 0.1 and ≤ 1.0 g / 10 min, as measured at 190 °C under a load of 2.16 kg in accordance with ISO 1133-1 (2011).

[0024] The recycled polyethylene formulation preferably comprises ≥ 90.0 wt%, more preferably ≥ 95.0 wt% of an ethylene-based polymer, based on the total weight of the recycled polyethylene formulation. The recycled polyethylene formulation preferably comprises ≤ 10.0 wt%, more preferably ≤ 5.0 wt% of a propylene-based polymer, based on the total weight of the recycled polyethylene formulation.

[0025] In a specific embodiment, the polymer composition may, for example, comprise ≥ 95.0 wt%, preferably ≥ 98.0 wt% of composition a), based on the total weight of the polymer composition.

[0026] The preferred polymer composition comprises an additive composition b) in an amount of ≥ 100 and ≤ 5000 ppm by weight, more preferably ≥ 200 and ≤ 2000 ppm by weight, even more preferably ≥ 500 and ≤ 1500 ppm by weight, based on the total weight of the polymer composition.

[0027] The polymer composition may for example comprise 2,2-bis(hydroxymethyl)-1,3-propanediol in an amount of ≥ 100 and ≤ 5000 ppm by weight, more preferably ≥ 200 and ≤ 2000 ppm by weight, even more preferably ≥ 500 and ≤ 1500 ppm by weight, based on the total weight of the polymer composition.

[0028] For example, the additive composition b) may comprise:

[0029] i. tris[2,4-bis(1,1-dimethylpropyl)phenyl]phosphite (CAS registration number 1065-97-0); and / or

[0030] ii. bis[2,4-bis-(1,1-dimethylpropyl)phenyl][4-(1,1-dimethylpropyl)phenyl]phosphite (CAS registration number 1000027-06-4); and / or

[0031] iii. bis[4-(1,1-dimethylpropyl)phenyl][2,4-bis-(1,1-dimethylpropyl)phenyl]phosphite (CAS registration number 1000027-04-2).

[0032] The preferred additive composition b) comprises:

[0033] i. tris[2,4-bis(1,1-dimethylpropyl)phenyl]phosphite;

[0034] ii. bis[2,4-bis-(1,1-dimethylpropyl)phenyl][4-(1,1-dimethylpropyl)phenyl]phosphite; and

[0035] iii. bis[4-(1,1-dimethylpropyl)phenyl][2,4-bis-(1,1-dimethylpropyl)phenyl]phosphite.

[0036] In a specific embodiment, the additive composition b) may for example comprise ≥ 90.0 wt%, preferably ≥ 95.0 wt%, more preferably ≥ 98.0 wt% of the sum of i, ii and iii, based on the total weight of the additive composition.

[0037] Preferably, the additive composition b) does not contain any phosphite compounds other than i, ii and iii. In a particularly preferred embodiment, the polymer composition does not contain any phosphite compounds other than i, ii and iii.

[0038] The additive composition (b) may further contain tris(2-propanol)amine, preferably wherein the additive composition (b) contains ≥0 and ≤10.0% by weight, more preferably ≥0 and ≤5.0% by weight, even more preferably ≥0 and ≤2.0% by weight of tris(2-propanol)amine, based on the total weight of the additive composition (b).

[0039] In an embodiment, the present invention also relates to the use of a formulation comprising 2,2-bis(hydroxymethyl)-1,3-propanediol and an additive composition comprising a compound of formula I:

[0040]

[0041] where each R is independently selected from 1,1-dimethylpropyl or hydrogen;

[0042] for reducing the amount of vinyl unsaturation in a polymer composition comprising an ethylene-based polymer, preferably wherein the polymer composition comprises a recycled polyethylene formulation.

[0043] The present invention also relates to an article comprising the polymer composition according to the present invention.

[0044] The present invention will now be illustrated by the following non-limiting examples.

[0045] Multiple polymer compositions were melt-extruded using a ZSK25 twin-screw melt extruder with a screw diameter of 25 mm and an L / D ratio of 40. The extruder was operated at 250 rpm, and the following set-point temperature profiles were used for each of the L1 - L10 zones of the extruder (where L1 is the feed zone and L10 is the die zone). Temperatures are in °C.

[0046] L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 160 210 230 240 240 240 250 250 250 250

[0047] The feed rate of the material to the extruder was 8.3 kg / h.

[0048] Using the above extrusion conditions, extrusion experiments were carried out on the material compositions, and the following materials were used.

[0049]

[0050] Using the above materials, the following compositions were used in the examples demonstrating the present invention.

[0051]

[0052]

[0053] To test the stability properties, each of Formulations 1 to 12 was subjected to 5 cycles of extrusion under the above - set conditions to establish the stability of the formulations when exposed to multiple melt - processing scenarios. Through this test, it was evaluated whether the formulations had the quality suitable for recycling applications.

[0054] In the following table, the test results of the vinyl index (VI) of the example formulations are presented.

[0055] VI 1 2 3 4 5 6 After the first cycle 1.93 1.79 1.72 1.65 1.56 1.52 After the third cycle 1.83 1.81 1.71 1.58 1.51 1.56 After the fifth cycle 1.87 1.79 1.74 1.55 1.51 1.51

[0056] VI 7 8 9 10 11 12 After the first cycle 1.91 1.80 1.73 1.56 1.50 1.49 After the third cycle 1.81 1.82 1.80 1.58 1.45 1.52 After the fifth cycle 1.81 1.84 1.79 1.56 1.52 1.51

[0057] The above results indicate that the polymer composition can reduce the vinyl index and also ensure that this reduction is maintained after multiple extrusions.

Claims

1. A polymer composition comprising or consisting of the following: a) A composition comprising at least one ethylene-based polymer; b) An additive composition comprising a compound of formula I: wherein each R is independently selected from 1,1-dimethylpropyl or hydrogen; and c) 2,2-bis(hydroxymethyl)-1,3-propanediol.

2. The polymer composition according to claim 1, wherein the ethylene-based polymer has: Density determined according to ISO 1183-1 (2019) of ≥ 940 and ≤ 975 kg / m 3 , preferably ≥ 950 and ≤ 970 kg / m 3 , more preferably ≥ 950 and ≤ 965 kg / m 3 ; and A melt mass flow rate (MFR2) of ≥ 0.1 and ≤ 5.0 g / 10 min, preferably ≥ 0.1 and ≤ 2.0 g / 10 min, more preferably ≥ 0.1 and ≤ 1.0 g / 10 min, measured at 190 °C under a load of 2.16 kg according to ISO 1133-1 (2011).

3. The polymer composition according to any one of claims 1-2, wherein the ethylene-based polymer has: A melt mass flow rate (MFR5) of ≥ 1.0 and ≤ 10.0 g / 10 min, preferably ≥ 1.0 and ≤ 7.5 g / 10 min, more preferably ≥ 1.5 and ≤ 5.0 g / 10 min, measured at 190 °C under a load of 5 kg according to ISO 1133-1 (2011); and / or A melt mass flow rate (MFR21) of ≥ 10 and ≤ 100 g / 10 min, preferably ≥ 20 and ≤ 75 g / 10 min, more preferably ≥ 25 and ≤ 60 g / 10 min, measured at 190 °C under a load of 21.6 kg according to ISO 1133-1 (2011).

4. The polymer composition according to any one of claims 1-3, wherein the ethylene-based polymer is an ethylene homopolymer or an ethylene copolymer comprising structural moieties derived from comonomers selected from 1-butene, 1-hexene, and 1-octene in an amount of ≤ 10.0 wt%, preferably ≤ 5.0 wt%.

5. The polymer composition according to any one of claims 1-4, wherein composition a) comprises a recycled polyethylene formulation, preferably wherein composition a) comprises ≥ 20.0 wt%, more preferably ≥ 40.0 wt%, of a recycled polyethylene formulation based on the total weight of composition a).

6. The polymer composition according to claim 5, wherein the recycled polyethylene formulation is a post-consumer recycled polyethylene formulation, preferably having: Density determined according to ISO 1183-1 (2019) of ≥ 940 and ≤ 975 kg / m 3 , preferably ≥ 950 and ≤ 970 kg / m 3 , more preferably ≥ 950 and ≤ 965 kg / m 3 ; A melt mass flow rate (MFR2) of ≥ 0.1 and ≤ 5.0 g / 10 min, preferably ≥ 0.1 and ≤ 2.0 g / 10 min, more preferably ≥ 0.1 and ≤ 1.0 g / 10 min, measured at 190 °C under a load of 2.16 kg according to ISO 1133-1 (2011).

7. The polymer composition according to any one of claims 5-6, wherein The recycled polyethylene formulation comprises ≥ 90.0 wt%, preferably ≥ 95.0 wt%, of an ethylene-based polymer based on the total weight of the recycled polyethylene formulation; and / or wherein the recycled polyethylene formulation comprises ≤ 10.0% by weight, preferably ≤ 5.0% by weight, based on the total weight of the recycled polyethylene formulation, of an acrylonitrile-based polymer.

8. The polymer composition according to any one of claims 1-7, wherein the polymer composition comprises ≥ 95.0% by weight, preferably ≥ 98.0% by weight, of the composition a) based on the total weight of the polymer composition.

9. The polymer composition according to any one of claims 1-8, wherein the polymer composition comprises ≥ 100 and ≤ 5000 ppm by weight, preferably ≥ 200 and ≤ 2000 ppm by weight, more preferably ≥ 500 and ≤ 1500 ppm by weight, of the additive composition b) based on the total weight of the polymer composition.

10. The polymer composition according to any one of claims 1-9, wherein the polymer composition comprises ≥ 100 and ≤ 5000 ppm by weight, preferably ≥ 200 and ≤ 2000 ppm by weight, more preferably ≥ 500 and ≤ 1500 ppm by weight, of 2,2-bis(hydroxymethyl)-1,3-propanediol based on the total weight of the polymer composition.

11. The polymer composition according to any one of claims 1-10, wherein the additive composition b) comprises: i. tris[2,4-bis(1,1-dimethylpropyl)phenyl]phosphite; ii. bis[2,4-bis(1,1-dimethylpropyl)phenyl][4-(1,1-dimethylpropyl)phenyl]phosphite; and iii. bis[4-(1,1-dimethylpropyl)phenyl][2,4-bis(1,1-dimethylpropyl)phenyl]phosphite.

12. The polymer composition according to claim 11, wherein the additive composition b) comprises ≥ 90.0% by weight, preferably ≥ 95.0% by weight, more preferably ≥ 98.0% by weight, of the sum of i, ii, and iii based on the total weight of the additive composition.

13. The polymer composition according to any one of claims 11-12, wherein the additive composition b) does not contain any phosphite compounds other than i, ii, and iii.

14. The polymer composition according to any one of claims 1-13, wherein the additive composition b) comprises tri(2-propanol)amine, preferably wherein the additive composition b) comprises ≥ 0 and ≤ 10.0% by weight, more preferably ≥ 0 and ≤ 5.0% by weight, even more preferably ≥ 0 and ≤ 2.0% by weight, of tri(2-propanol)amine based on the total weight of the additive composition b).

15. Use of a formulation of an additive composition comprising 2,2-bis(hydroxymethyl)-1,3-propanediol and a compound of formula I: wherein each R is independently selected from 1,1-dimethylpropyl or hydrogen; for reducing the amount of vinyl unsaturation in a polymer composition comprising an ethylene-based polymer, preferably wherein the polymer composition comprises a recycled polyethylene formulation.

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